Lemon tree named ‘Glueck’

ABSTRACT

A new and distinct variety of lemon named ‘Glueck’ characterized by producing mature fruit with a juice having a lemon flavor and a high sugar-acid ratio.

Latin name of the genus and species of the plant claimed: Citrus limon.

Varietal denomination: ‘Glueck’.

BACKGROUND OF THE NEW VARIETY

The present invention refers to a new variety of lemon which will hereinafter be denominated as the ‘Glueck’ lemon tree. The ‘Glueck’ lemon tree produces lemon fruit that taste like lemon, but have juice with a high sugar-acid ratio, producing a lemon flavor without the sourness associated with lemon juice.

ORIGIN AND ASEXUAL REPRODUCTION OF THE NEW VARIETY

The invention (variety) comprises a new and distinct variety of a lemon tree discovered by the inventors in a cultivated orchard on the Finca Los Pocitos property in the Tucumán province of Argentina, which was purchased in 1993, and subsequently continuously owned, by the Applicant. Specifically, while working on the Finca Los Pocitos property, the inventors discovered the new cultivar and scion buds were removed from the identified trees for grafting onto Troyer citrange “Troy” rootstock (unpatented), which is a hybrid of Citrus sinensis and Poncirus trifoliate, to form a second generation. The new cultivar is believed to a spontaneous mutation of a lemon tree grown in the cultivated orchard. From the second generation, trees were selected on the basis of fruit superiority and growth parameters and scion buds were removed from the selected trees for further asexual reproduction by grafting to form a third generation. The new cultivar was subsequently asexually reproduced by the inventors in the Tucumán province of Argentina by grafting on a variety of root stocks, including Citrumelo Swingle CPB 4475 (Poncirus trifoliata x Citrus paradisi), Citrange C-35 (Citrus sinensis ‘Ruby’ orange x X Citroncirus webberii ‘Webber-Fawcett’ trifoliata), and 79 AC (Citrus reshni Hort. ex Tan. x Citrus paradisi Macf. x Poncirus trifoliata (L.) Raf.). This year the new cultivar was also grafted on Poncirus trifoliata ‘Rubidoux’ and Flying Dragon (Poncirus trifoliata var. ‘Monstrosa’) root stock. The inventors carefully compared all of the asexually reproduced trees with the originally discovered trees and found the fruit to be substantially identical in all distinctive respects through several generations of asexual reproduction including on different root stocks. The discovered cultivar has been shown to remain true to type in successive generations of such asexual reproductions.

In comparison with conventional lemon trees, the fruit of the present variety has a higher sugar-acid ratio, resulting in a fruit having a juice with a lemon flavor but lacking the sour acidity associated with typical lemon fruits.

SUMMARY OF THE NEW VARIETY

The ‘Glueck’ lemon tree is particularly characterized by producing fruit with a high sugar-acid ratio, with a fall of fruits in December, with good fruit size.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a color photograph of the general appearance of the plants.

FIG. 2 is a color photograph of a section of bark.

FIG. 3 is a color photograph of a young branch with leaves and terminal floral bud.

FIG. 4 is a color photograph of floral buds to terminal pairs and solitary axillary.

FIG. 5 is a color photograph of a fully open flower.

FIG. 6 is a color photograph of a gamosepalous calyx and gynoecium on a nectariferous disc.

FIG. 7 is a color photograph of stamens wielded by the filament, free stamen, and staminode.

FIG. 8 is a color photograph of a branch with thorns and fruit.

FIG. 9 is a color photograph of several leaves.

FIG. 10 is a color photograph of a leaf showing essential oil glands of a leaf.

FIGS. 11 is a color photograph of a branch with fruits in various stages of maturity.

FIG. 12 is a color photograph of the morphological aspects of different fruits.

FIG. 13 is a color photograph of a straight base of a fruit with persistent calyx in the form of rudiment.

FIG. 14 is a color photograph of an apex with a nipple-shaped protuberance of a fruit with poorly defined areolar groove and the remains of a persistent style.

FIG. 15 is a color photograph of average sections of fruit.

FIG. 16 is a color photograph of glands of essential oils present in the peel of a fruit.

FIG. 17 is a color photograph of a cross-section of fruit where the flavedo (exocarp) and albedo (mesocarp) of the husk can be seen.

FIG. 18 is a color photograph of the axis of a fruit.

FIG. 19 is a color photograph of a seed of a fruit.

FIG. 20 is a black and white microphotograph of lenticels in the bark.

FIG. 21 is a black and white microphotograph of an essential oil gland.

DETAILED BOTANICAL DESCRIPTION

It should be noted that the described characteristics may vary depending on agricultural practices and climatic conditions, location and season. The quantitative values set forth below are expressed as an average value, which is obtained from the specimens analyzed. Quantitative traits were taken from each of four specimen trees. The angles of divergence of the fruit branches with respect to the main axis were calculated by means of scale photographs.

Twenty fully developed leaves were selected from each specimen, considering the fifth leaf from the apex in orientation N, S, E, W and in good phytosanitary conditions. They were measured and photographed with a digital camera to calculate quantitative data. To determine the venation, size, and density of essential oil glands, the diaphanization and clarification technique was performed according to C. Dizeo de Strittmatter, “Nueva técnica de diafanización,” Bol. Soc. Arg. Bot. 15, 126-129 (1973) and later stained with 1% cresyl violet, as per G. E. Zarlaysky, “Histologia vegetal: técnicas simples y complejas,” 1a ed. Sociedad Argentina de Botánica, Buenos Aires (2014).

Ten flower buds were taken from each specimen in development stage medium and ten flowers in were taken in maturity stage (open corolla). These were measured and photographed to calculate quantitative values.

All observations of fruits and their parts were made at the optimum maturity stage. The characteristics described below correspond to the average of ten fruits and their respective seeds of each specimen.

Quantitative values were calculated directly through the use of calibrated measuring tape (TJIMA 30 m) and vernier caliper using scale photographs (made with a KODAK digital camera Az-252 16 mpx). Micromorphological values, surfaces, and angles were calculated using a Zeiss Stemi-2000C stereo microscope with a Zeiss Axiocam ERc 5s digital camera attached and AxioVision software version 4.8.2 (Carl Zeiss Ltd, Herts, UK). All values are expressed as mean values and standard deviation.

The descriptions of foliar traits and shapes were made following B. D. Ellis, C. Daly, L. J. Hickey, H. R. Johnson, J. D. Mitchell, P. Wilf, S. L. Wing, “Manual of leaf architecture,” Cornell University Press, USA (2009)

The colors are described in reference to The 2005 Royal Horticultural Society mini color chart.

The determination of sugars and acidity in juice was carried out in concentrated juice (10 mL) for each specimen by titration with 0.1 N sodium hydroxide and 1% phenolphthalein. The specifications by the Department of Primary Industries and Regional Development Agriculture and Food of the Government of Australia were followed.

The titration was monitored by color change and pH change up to 8.2-8.4.

Phenotypic Description of Citrus limon ‘Glueck’.

-   Tree:     -   -   Size.—Medium size. Height: 4.19±0.13 m high (0.25 to 0.35 m             corresponding to the Troy rootstock) Width: 6.06±0.53 m wide             at the crown level.         -   Vigor.—Specimens are medium-vigor mature trees, the presence             of aphids and leaf spots is detected. Tolerance to winter             conditions and drought are expected to be the same as those             of the rootstock.         -   Flowering.—First flowering occurs in August and full             flowering in September, while the fall of fruits is expected             for December. -   Trunk:     -   -   Size.—Rootstock has a diameter of 0.60±0.02 cm and a trunk             0.58±0.04 cm in diameter, 30 cm above the rootstock (FIG.             1).         -   Bark.—Dark brown soft texture bark (RHS 165A) with dark             brown (RHS 200A) to black (RHS 186A) veins (FIG. 2).         -   Lenticels.—Scarce evidence of lenticels of approximately 1             mm, dark brown (RHS 200A) to black (RHS 186A) color, and             several in number (2 to 4/cm²) (FIG. 20). -   Branches:     -   -   Canopy.—Spherical somewhat irregular canopy, with open             branches at the center.         -   Length of branches.—The fruit branches located one meter             above the rootstock measure 1.8±0.54 m in length by             12.5±9.19 cm in diameter in their middle section,         -   Angle of branches.—Acute to straight angles of divergence             (35.23° to 90.07°) with respect to the stem.         -   Color of branches over 2 years old.—Branches over 2 years             old have a color similar to the dark brown stem (RHS 165A)             with dark brown (RHS 200A) to black (RHS 186A) veins.         -   Color of branches less than 2 years old.—Younger branches of             less than 2 years not lignified have green color RHS139C to             RHSC 137C.         -   Thorns.—Present. Straight thorns 1.75±0.88 cm long, present             in a density of 0.6 to 0.3/cm² (FIG. 8). -   Leaves: The specimens have simple leaves that are notophyllic     (approximately 33.08±8.78 cm²).     -   -   Length.—10.43±2.25 cm.         -   Width.—5.54±1.11 cm wide (having a length/width ratio 1.87).         -   Color.—Dark green blades (RHS 137A) are found on the upper             surface and light green blades (RHS 146C) are found on the             underside.         -   Shape.—Alternating, membranous, smooth, symmetrical             elliptical shape in their middle section.         -   Base.—Obtuse to acute base (angle 92.82° to 58.61°) that is             wedge-shaped, decurrent, and symmetrical, with a crenated             edge.         -   Apex.—Acute to obtuse apex (angle 80.33° to 143.24°),             generally straight to shortly acuminate, occasionally             rounded or retuse (slightly emarginated), in the latter case             it seems to be associated with the activity of herbivorous             insects (FIGS. 3 and 9).         -   Essential oil glands.—Translucent, distributed on the             surface and leaf margins, with a density 1-2/mm², diameter             139.40±25.72 μm, with larger dimensions in the recesses of             the margin of the blade (diameter 275.22±45.69 μm) (FIG. 10)             (See also FIG. 21).         -   Color.—Coloring of anthocyanins in young leaves is absent;             they display a greenish yellow color (RHS 145A) in the upper             surface and greenish yellow (RHS 145B) on the underside             (FIG. 9).         -   Petioles.—Wings: Unwinged. Color: dark green (RHS 137A), in             section terete to subterete with adaxial ribs of scarce             development. Length: 1.10±0.26 cm in length. Diameter:             1.66±0.26 mm in diameter in the dorsiventral plane of its             middle section (FIG. 9).         -   Veins.—Pinnated eucamptodromous brochidodromous venation,             with a single primary vein that is straight unbranched.             Color: green (RHS 136A). Width at 1 cm from the apex:             0.23±0.5 mm. Width at the base 1 cm from the junction with             the petiole: 1.40±0.21 mm. -   Flowers: Flower buds, alone or in groups of 2-3, terminal or     axillary, are observed (FIGS. 3 and 4).     -   -   Floral bud.—Shape: oval. Length: 12.75±2.24 mm. Diameter:             6.18±1.05 mm in diameter in its middle section. Color: white             (RHS 155D), with dark pink (RHS 53C) to pink spots (RHS             64D).         -   Calyx.—Gamosepalous dome-shaped calyx having 5 sepals             (segments). Color: yellowish green (RHS 149C), Length:             8.18±0.94 mm. Width: 5.45±0.54 mm in width in each segment.         -   Flowers.—Perfect hermaphrodite flowers. Diameter when fully             open: 3.02±0.19 cm (FIG. 5). Aroma: orange blossom.         -   Pedicel.—Brief. Color: light green (RHS 140D). Length:             0.54±0.05 cm. Diameter: 0.14±0.05 cm.         -   Sepals.—Gamosepalous dome-shaped calyx has 5 sepals,             acuminate. Apex: acute apex (RHS 149C). Length:             9.17±0.83 mm. Width: 5.57±0.54 mm in each segment (FIG. 6).         -   Petals.—Dialypetalous corolla has 5 petals. Shape: elliptic             elongated oblongs in arches. Apex: acuminate to rounded,             acute apex. Margin: smooth. Color: white (RHS 155D). Surface             area: 0.66±0.11 cm². Length: 1.95±0.27 cm. Width: 0.64±0.10             cm.         -   Pistil.—Gamocarpellary gynoecium, arranged on a             nectariferous disk. Number of stigma: single capitated             globose stigma. Stigma color: light yellow (RHS 20A). Stigma             thickness: 1.23±0.42 mm. Stigma diameter: 1.60±0.43 mm.             Style: single linear apical style. Style color: light             yellowish towards the apex (RHS 4D) to purplish pink at the             base (RHS 71B). Style length: 5.98±1.03 mm. Style diameter:             1.35±0.15 mm in its middle section. Ovary color: yellowish             green (RHS 145C). Ovary position: superior. Ovary shape:             spherical. Ovary length: 2.05±0.10 mm. Ovary diameter:             2.26±0.21 mm in diameter in its middle section (FIG. 6).             Ovary Locules: In cross-section, ten locules were observed             per ovary. Ovary ovules: numerous ovules of axial             placentation.         -   Stamen.—Polyadelphous androecium. Number: 43-56 stamens with             1-3 staminodes, in one or two cycles. Filaments: free or             welded by 6-9 flattened filaments of 12.81±mm of total             length. Anthers: Two-teaked. Anther color: light green (RHS             140D). Anther length: 2.3±0.2 mm. Anther diameter:             0.58±0.09 mm. (FIG. 7). -   Fruit: Hesperidium. fruit are genuine, monothalamic, fleshy,     indehiscent. -   External characteristics.     -   -   Color.—Yellow (RHS6A) with greenish yellow coloration at the             end of the nipple (RHS149A) (FIGS. 11 and 12).         -   Shape.—Elliptic-oval shape. Length: 7.99±0.64 cm. Diameter:             5.99±0.60 cm in diameter in its middle section, where it has             the largest diameter.         -   Weight.—Average weight 116.01±32.28 gr (FIG. 12).         -   Base.—Straight or with a short neck or collar (0.5±0.2 cm in             length).         -   Calyx.—Persistent, in the shape of a rudiment (FIG. 13).         -   Apex.—Nipple-shaped protrusion of 1.03±0.21 cm in length by             1.33±0.24 cm in diameter is found at the base.         -   Stylar scar.—Less than 1 mm in diameter and sometimes with             remains of persistent style (FIG. 14), frequently             accompanied by an undefined areolar groove of 2.54±0.31 cm             in diameter.         -   Husk.—Surface: smooth husk, evidently glandular. Thickness:             3.5±0.8 mm (flavedo and ectocarp 1.0-1.5 mm and albedo or             mesocarp 1.7-3.3 mm). Glands: 520.81±137.16 μm in diameter.             Gland density: average density of 60 glands/cm2. Color:             yellow exocarp (RHS6A) and white mesocarp (RHS 155D) (FIGS.             15, 16, and 17). -   Internal characteristics:     -   -   Flesh color.—Yellow (RHS12A).         -   Interior segments.—9.29±1.04 (FIGS. 15 and 16).         -   Interior segment membranes.—Moderate resistance.         -   Septa.—Equal number as sgments. Thickness: 0.2 to 0.3 mm.         -   Vesicles.—Cylindrical. Length: 1.5±0.5 cm. Diameter:             0.26±0.05 cm in their widest section.         -   Axis.—Solid to semi-hollow. Diameter: 0.56±0.12 cm (FIG.             18).         -   Seeds.—Each fruit has an average of 9.45±3.50 seeds of which             1-2 can be aborted. Length: 10.75±1.4 mm. Width:             5.75±0.66 mm. Shape: elliptical to ovate shape. Surface:             smooth. Color: white (RHS155D) with a violet-pink collar at             the base (RHSN77D) (FIG. 19).         -   Juice.—Color: yellow (RHS4A). Total sugars: 8.22±0.49° brix.             pH: 5.51±0.09. Acidity: 0.054±0.10 equivalents of citric             acid. Sugar-acid ratio: 150:1. Flavor: lemon.

mL of Percentage 0.1N of citric Sugar:acid Plant pH ° Brix NaOH acid** ratio 1 5.62 8.9 0.8 0.051  174.5:1 2 5.55 8.3 0.9 0.057 145.61:1 3 5.44 7.9 0.8 0.051  145.9:1 4 5.46 7.8 0.9 0.057 136.84:1 Average 5.51 ± 8.22 ± 0.85 ± 0.054 ± 152.96 ± 0.09 0.49 0.05 0.10 16.14 **Percentage of citric acid: volume of NaOH used × 0.064. 

We claim:
 1. A new and distinct variety of lemon tree as described and illustrated called ‘Glueck’ that is characterized as producing fruit with a juice having a lemon flavor and a high sugar-acid ratio. 